This invention relates to centrifuges, and more particularly, relates to centrifuges and circuitry therein.
Automated centrifuges, such as taught in U.S. Pat. No. 4,567,373, filed Oct. 20, 1982, automatically monitor a sample during centrifuging and provide data points indicative of a desired characteristic of the sample that is being tested during the centrifuging. More particularly, these automated centrifuges may image the position of fluids or fluid interfaces in a sample holder as it rotates. Such automated systems minimize manpower needs and provide a plurality of data points at predetermined intervals throughout the centrifuge run.
Further, a computer may be employed to analyze the data in real time to provide an output indicative of the amount of fluid or fluids produced by the sample during centrifuging. Such centrifuges typically employ a strobe that provides light, or other types of radiation, which impinges on the sample holders or collection tubes. The light impinging on the collection tube may then be collected by suitable detector array. However, it must be possible to identify and align the respective sample holders with index marks as is known in the art, to appropriately allow for imaging the proper holder in the proper time sequence.
Conventional centrifuge strobe firing circuits usually fire only when the holder of interest is detected as overhead or below the strobe. However, due to the intrinsic delay in the detecting and firing circuit, this leads to a "forward creep" of the tube image with increasing centrifuge speed. The magnitude of this forward creep increases with increasing speed until the tube image may completely move out of view of the appropriate detectors. Previous attempts to solve this problem have consisted chiefly of requiring the operator of the centrifuge to visually review the flash position of the strobe relative to the holder and via appropriate mechanical manipulation of the strobe, reposition the strobe to continue flashing on the desired holder. The term "flash" is used herein to means the time at which a stobe reaches its maximum brightness. However, such adjustment by the operator may be required for several different speed ranges as the speed of the centrifuge is gradually increased. These continuing attentions of the operator to the flashing of the strobe and operation of the centrifuge defeats an important objective of the automated centrifuge, i.e. relieving the operator of the tedium of attending to the operation of the centrifuge.
These and other limitations and disadvantages of the prior art are overcome by the present invention, however, and improved methods and circuitry are provided for automatically preventing image creep in a centrifuge as its speed is increased from low speed to maximum speed.